Bicycle Mechanics - What Size Seat Clamp?

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fixedkicks

11-10-10, 08:43 PM

I just got a frame fitted for a 27.2 seatpost. I have never had a bike that has to have a seat clamp added to its frame before,

MY QUESTION IS... do i need a seat clamp that is also sized 27.2, or since the clamp is going on the frame does it need to be larger

FBinNY

11-10-10, 09:34 PM

Seat post clamps are sized by the outside diameter of the frame's seat tube, not the seat post which is the size of of the inside diameter. They are often sold in metric sizes, but these are actually rounded off equivalents of standard inch sizes, either 1-1/8", 1-1/4", or 1-3/8" (approx 28..6, 31.8, or 35mm).

If the seat post is 27.2, odds are the seat tube is 1-1/8" if steel or 1-1/4 if aluminum or carbon, but you'd best either measure or check the spec sheet to be sure.